Physical activity has a well understood set of benefits. UK leisure time physical activity (LTPA) is socially patterned, with lower socio-economic groups participating less. There is evidence from the literature that in addition to structural causes, there may be a ‘working class’ worldview of LTPA, which strongly influences their lack of participation. Thus, a theoretical approach for social marketers is advocated based on class culture. This approach, which centres on Bourdieu’s habitus, views problem behaviours in terms of class-based dispositions rather than individualistic intention, attitude and decision making. This research used an ethnographic mixed-method approach to explore the habitus of five case study families on a deprived estate. Findings suggested that their perception of LTPA was negative, or else they dismissed it as a leisure option. They preferred sedentary behaviours which matched their observed goals; of ‘family survival’, ‘image management’, ‘instant pleasure’ and ‘withdrawal through fantasy’. These rich insights, into the lives of particularly hard-to-reach families, are the first contribution of this PhD to the social marketing field. However, the theoretical approach taken also enabled a retroductive analysis (based on critical realist thinking) to explore hitherto invisible mechanisms which may be part of the observed habitus, and may have affected the observed dispositions towards LTPA. These were ‘lack of perspective’, ‘lack of control’ and ‘lack of participation’. Also, the theoretical conceptualisation of LTPA as a ‘culturally signifying practice’, embedded in the class cultural habitus, has enabled the researcher to explore three potential social marketing responses to the findings. These are the traditional approach based on exchange; the community-development approach of ‘habitus change’; and finally, environmental approaches, grounded in ecological theory and behavioural economics. The ethical and ideological contentions of these approaches for social marketers are discussed, and it is recommended that social marketers expand their strategic options to address powerful habitus effects.